1. Field
This invention relates in general to boot systems utilizing a relatively stiff outer shell and a removable flexible inner liner, and particularly to sport boots such as used for the sports of skiing and snow boarding.
2. State of the Art
Over the past several years, ski boots have evolved through several stages from stiff unlined boots of leather to the present rigid outer shells (generally of plastic) with flexible inner liners of various types. For use with modern bindings, it is essential that the outer shell be stiff to optimize the control effected on the skis by a skier shifting his weight or the attitude of his feet. The inner liner provides for adequate comfort so that the skier can tolerate wearing the boots for extended periods. Similar considerations are involved in the design of other sport boots, notably those used for snow boarding.
Various ski boot inner liners are disclosed by U.S. Pat. Nos. 4,078,322; 3,786,580; and 4,038,762; the disclosures of which are incorporated by reference for their teachings concerning the construction of ski boot inner liners generally. FIG. 1 of U.S. Pat. No. 4,078,322 illustrates a representative outer shell and inner liner ski boot system as typically assembled for use.
Several approaches to inner liner construction have been tried to achieve the desired combination of foot support, ease of forward ankle movement, and adequate comfort for the skier. Thus far, no approach has been entirely successful. U.S. Pat. No. 4,078,322 is generally instructive, and FIG. 3 of that patent discloses a representative currently available inner liner. The assembly line manufactured liner disclosed is removable from an associated outer shell. It is constructed of a soft closed-cell (i.e., micro cellular) foam material. Closed-cell foam provides cushioning, support, and insulation to keep a skier's foot comfortable and warm for extended periods of time. Spacing tabs are provided in the vicinity of the lower ankle to ensure a snug fit around the heel, and the liner is slit down the front to facilitate foot entry without a tongue. Avoiding the use of a tongue provides a substantially continuous smooth inner surface against the front of a skier's leg, and eliminates the discomfort that routinely occurs when the edges of the tongue of previous ski boot designs press into the front of a skier's leg. Even greater discomfort may be experienced if the tongue happens to slip to the side, with repeated flexing of a skier's ankles.
While the tongueless design represents an improvement in comfort to the user, some discomfort remains due to the presence of the seam formed on closing the front entry slit. Front closure seams are inevitably distorted into bumps or ridges in the high pressure area at the front of a skier's leg as the skier flexes his ankles while skiing. Another problem associated with the front entry tongueless design is the difficulty associated in opening the liner sufficiently, especially while restrained by the surrounding boot shell, to easily insert a foot. Typically, the ball of a skier's foot is much wider than the liner ankle area it must pass through to gain entry into the assembled boot.
Foam inner liners are highly desirable for the warmth, comfort, and support they can provide. However, the liner wall thickness associated with such liners creates resistance to the forward ankle flexure which is necessary for proper control of skis. There remains the need in ski and other sport boot inner liners for increased forward flexibility, increased comfort at the front pressure point of a participant's leg, and improved foot access to the interior of the liner.
Inner liner systems have been sold with ski boots for many years. Various techniques have been used to custom fit inner liners to individual feet; such as manufacturing design modification of assembly line produced liners, use of fitting pads, or totally custom molded liners; as disclosed in U.S. Pat. Nos. 4,078,322, 3,786,580, and 4,038,762, respectively. This invention provides improvements in design applicable to any of these inner liner systems.